This is an excellent idea! I don't have a great place to mount the jacks, so I think I'm going to mount an old router or switch in my free-standing coat closet and plug my keys into it instead. I'll upload an image when I get it finished. Very cool.

actually you can get 56 combinations from your configuration because 7-8 is not the same as 8-7, this is why:an LED is a diode, it allows current flow in one direction only. which means you can use each combination with inverted polarities to give you double the combinations. for example, if 7 i connected to GND and 8 is connected to +V, an LED with the anode connected to 8 and cathode connected to 7 will light up but an LED with the anode connected to 7 and the cathode connected to 8 will not light up, thus giving you double the combinations.

if you want to use 2 LEDs, you can get 14 combinations:lets say you connect the LEDs to pin 1 and 4, pin 1 will be connected to GND and pin 4 to +v, all other pins will be connected to -V, for this to work you will need 2 LEDs connected in parallel with different polarities (green has cathode connected to 1 and red has anode connected to 1).what this means is that when connected to the correct port, the green LED will light up because its anode is connected to +v and catode is connected to GND, the red LED will not light up because its catode is connected to +v and anode is connected to GND (which creates current flow in the wrong direction). whan connected to the wrong port, the +v pin is not aligned the LEDs pin causing the LEDs pin to connect to -V. the red LED will light up because its anode is connected to GND and catode is connected to -V (current flow is from GND to -V, as opposed to +v and GND where the current flows from +v to GND), the green LED will not light up because of the same reason as before.for this to work you will need a common GND pin for all combinations, this will give you 7 combinations and if you invert the polarities on the LEDs and on the circuit (+v and -V) you get 14 combinations.

i haven't figured out how to use dual-colored LEDs yet.you could also use a microcontroller like an arduino to trigger an alarm or display a number or text on an LCD for each plug or even report to Twitter.

Good thinking - except for the twitter part. I see no reason to tell the world that you just took your car and house key out. Kinda says "I'm out of my house for a bit - come rob me."

On reflection, 7-8 IS the same as 8-7 because its only wire in the plug. You're talking about putting the LED in the plug, which was not part of my design. I intended on putting the LED above the socket, so its permanently wired into the wall panels.

it doesn't have to update your twitter account and it doesn't have to say anything revealing, it can report to it's own account just for your remote monitoring. kinda like the twitter-reporting-roomba - who cares when roomba finishes cleaning your bedroom?! you do.and it was just an example of the marvelous things you can do with a simple microcontroller.

you're thinking of using the plug as a jumper, in that case, 7-8 is the same as 8-7.what you can do to have the best of both worlds is to connect a simple diode between the pins. that way you get a polarized jumper that will only light an LED with the right orientation - giving you twice the combinations with socket mounted LEDs.

another thing you can do is not use a common pin on the LEDs (like your initial design implies) and use 2 jumpers inside the plug, giving you more combinations, if you implement the first idea of a polarized jumper (you can use one diode on one jumper, no need for two) you get, once again, twice the combinations.

i only see one problem with using the plug as a jumper - you can only connect one (or two) wire(s) inside the plug, meaning there are only one or two wires in the loop that hold the key. i think that will be a little flimsy, unless you use some CAT7 wires or something.

i think i'll revisit this instructable and try making this work. (just received 1000 green LED in the mail this week, time to put them to good use :) )hope i'll find the time...

Absolutely LOVED this instructable!!!! So much that I decided to feature it on my website. You can see the page here:http://www.lescreateliers.com/Les_Createliers/Idees_Ideas/Entries/2011/9/8_Porte-cles_et_support_RJ-45RJ-45_key_chain_%26_rack.htmlIf, for any reason, you do not wish to appear on my website, just let me know and I'll remove my post right away.

A suggestion for the wall hanging part is to use the ports from old/dead hubs, switches or routers. You could remove the port groups from the circuit board and put them in a custom case. Most hubs/switches have clusters of 4 or 6 ports that could be arranged in various ways to provide spots for countless keys.

I do a lot of cable termination, and have fell in love with the EZ-RJ45 plugs from MilesTek. lets you feed the wires through the plug and crimp and trim in one go!I've got some leftovers from a recent project, I'll definitely need a key fob like this!http://www.milestek.com/C-1203-ez-rj45-termination-system.aspx

1) make sure one of the wires connects pins 1->2.2) Hook up either a battery or a transformer for DC power (make sure the voltage is compatible w/ the LED, else you'll need a resistor hooked up in serial w/ the LED) , and connect its positive lead to pin 1 on the jack.3) Connect the LED to pin 2 on the jack, and to the negative lead from the battery/transformer.

You could also make creative use of a transistor such that it lights up an LED (different one?) when you unplug the keyring. Would be nice for hanging up the key in the dark.

you know if you really wanted to take this far(probaly too far) you could hook these up to something(as others have said a switch) essentially loop back, but then have monitoring software, then you could either feed those to a set of lights somewhere so you can see who's home(or what vehical is free) or really geeky would be set up a webserver based on the status of the keys......

Could also follow this to colour code the cables if you don't want to buy loads of different colours?

http://www.youtube.com/watch?v=1ITGM1XILb4

Not sure if it would be any cheaper, but you could buy a longer single colour instead of multiple different colours and save the cable for anything else you need it for?

Work may even have a few/some cables lying around ready to be thrown out, just need the plugs and protectors for the key loop then. You could possibly even talk to the IT guys and see if they have a crimper you could use while at work?

As a non-tech type person, I have to ask, where do you get the jacks and plugs? I like your idea and I'd like to put it to use but I'm lost. I suppose I can get the jacks from some old ethernet cables but I don't know where to get the plugs.

Depending on where you live, a Lowes or Home Depot will have what you need.Pretty sure an Ace will have it as well. The cable ends, the crimper, and wire should be available. Although for the wire you could pirate out of an existing cat5 cable.(Destroying the cable, but hey, new keyring.)

No real tech knowledge needed, although experience getting those little wires into the jack end for crimping will be helpful.

I would also say careful about how many keys you put on each jack. Those wires are pretty small.